pandroid: Android keycode state is just a bool

Don't make serialization difficult with a useless struct
pandroid: savevm handler for goldfish_events
pandroid: add cpu_memory_rw for goldfish_nand
Goldfish's NAND hardware is writing to virtual addresses.
Worse, it was doing so in a way that evaded record/replay capture.
Pandroid: use cpu_memory_rw() in all goldfish hw that touches virtual memory.
ARM: support mem callbacks on ARM